Selective call receivers, such as, for example pagers, for displaying messages are well known. A selective call receiver typically includes electronic circuits for receiving a transmitted message, for alerting a user that a transmitted message has been received, and for displaying the transmitted message on a display. It has been found that it is more efficient to transmit and receive long messages with communication protocols that use message fragmentation to redistribute traffic over a series of time slots. U.S. Pat. No. 5,311,516 describes a communication system including a selective call receiver that is capable of receiving a plurality of message packets of a transmitted fragmented message, wherein each message packet includes an address and message data. The message data can include an indication of whether more message packets are to be received to complete the fragmented message. The selective call receiver correlates the address of each message packet to a predetermined address, decodes the message data of each message packet, and then successively stores the decoded message data to reconstruct the fragmented message.
Some selective call receivers also have the capability to receive and display a message in any of a variety of scripts. For example, U.S. Pat. No. 5,107,259 describes a selective call receiver that includes a decoder that recognizes a script select character embedded within message data of a received message. A font memory stores fonts corresponding to the scripts. The fonts may include an alphanumeric font requiring a first resolution, for example one byte per character, and an ideographic font requiring a second resolution greater than the first resolution, for example two bytes per character. A controller in the form of a microcomputer is coupled between the font memory and the decoder for selecting one of the fonts in response to the script select character. A display is coupled to the controller for displaying the message in the selected font.
In some cases, a message packet from a fragmented message is lost. Typically, this will mean that a portion of the fragmented message containing the message data from the lost message packet will be missing but that the remainder of the fragmented message can be displayed normally. A more serious problem arises in the case where a fragmented message is received and a message packet containing one or more script select characters is lost. The beginning of the message containing message data from the initial message packets typically will be displayed in the proper font. However, message data from message packets subsequent to the lost message packet may be displayed in a wrong font. This can garble the remainder of the message beyond recognition.
Thus, there is a need for a selective call receiver that is capable of displaying a garbled message fragment of a fragmented message in a readable script.